Boat hull with tunnel structure

Abstract

A boat hull having a tunnel structure along the bottom of the hull in the form of a truncated hollow partial cone indentation parallel to the keel of the boat. The tunnel has a truncated end attached to the bottom of the hull near the keel and an open end attached to the transom of the boat. The tunnel encloses a propeller shaft extending from the boat interior at the truncated end, the propeller shaft, a propeller and a rudder. The angle of the cone with respect to the keel places the propeller about 45% to 50% within the tunnel at planing attitude or speed. The combination of the tunnel placement along the hull and the axis of the propeller shaft increases the efficiency of the boat and reduces fuel consumption.

I claim:  
     
       1. A hull structure for a boat, said hull having a bottom, a bow, a stern, and a keel extending at least partially from said bow to said stern along said bottom, a propeller shaft extending from the interior of said hull through said bottom and toward said stern from between said bow and said stern, said hull structure comprising: 
       a) a tunnel along said bottom of said hull, said tunnel presenting a truncated partial cylindrical cone shaped hollow surface indentation along said bottom of said hull, said cone having a central axis and a cone angle with respect to said central axis, the smaller forward end of said cone extending toward said bow and the enlarged trailing end of said cone extending toward said stern,  
       b) said end of said cone at its forward end being truncated with an end closure and connected to said hull bottom to provide a substantially normal connection between said truncated end and the axis of said propeller shaft extending through said end closure and boat bottom and into said tunnel,  
       c) the cone angle of said cone being constant from said connected truncated end toward said stern,  
       d) said cone being attached to said bottom along its exterior surfaces extending to said stern and ending in attachment of said trailing end to said stern to establish said hollow tunnel,  
       e) the central axis of said cone being aligned with said bottom and having said cone angle of about 6° to 12° with respect to said cone axis and said bottom.  
     
     
       2. The hull structure of  claim 1  wherein said propeller shaft extending through said bottom of said hull extends through said truncated end closure of said cone and within said cone at an angle of about 1° to 5° downward with respect to said hull bottom. 
     
     
       3. The hull structure of  claim 2  wherein said propeller shaft extending through said truncated end closure of said cone extends at an angle of about 5° to 10° with respect to the interior surface of said cone. 
     
     
       4. The hull structure of  claim 1  wherein said propeller shaft passing through said substantially normal connection through said truncated end closure of said cone toward said hull bottom extends at about 1° to 4° downward with respect to said cone axis. 
     
     
       5. The hull structure of  claim 1  with the addition of a propeller shaft support strut within said cone, said strut adapted to support said propeller shaft forward of said cone attachment to said stern. 
     
     
       6. The hull structure of  claim 1  wherein said hull bottom is provided with a pair of said tunnels along said bottom, said tunnels being spaced equally on each side of said keel. 
     
     
       7. The hull structure of  claim 1  wherein said hull is a hydroplane with side sponsons and a central flat bottom, said tunnel is an indentation along said central flat bottom. 
     
     
       8. The hull structure of  claim 1  wherein said hull is a trimaran with side hulls and a central hull, said tunnel is an indentation along said central hull. 
     
     
       9. The hull structure of  claim 1  wherein said hull is a catamaran with side hulls and a central hollow area, said central hollow area including a support structure for said tunnel indentation. 
     
     
       10. The hull structure of  claim 1  wherein said hull is a catamaran with side hulls and a central hollow area, each of said side hulls having a tunnel indentation. 
     
     
       11. The hull structure of  claim 1  wherein said truncated partial cylindrical cone shaped hollow surface indentation is about 4 inches in radius at said forward truncated end closure connection to said bottom, said indentation is about 7 to 8 inches in radius at said stern connection, said cone indentation length from said connection of said truncated end closure to said bottom at said attachment to said stern is about 60 inches, whereby a propeller of suitable size for said cone indention and driven by said propeller shaft and supported about 24 inches from said stern is in a position with about 45% to 50% of said propeller rotating within said indentation.